Separation of orgsnic issuers



Patented June 3, 1952 Alfred W. WeitkamD, Whiting, {and Norman}. Bowman,Gary, Ind assignors to Standard -il Company, Chicago, 111.,

Indiana a corporation of NoDrawin'g. i lpplicatiomseptember3ll,1948,Serial No. 52,122

This invention relates to the separation oi organic acids, and to theseparation of organicacid esters. fMore particularly, it relates to thesegregation of various types of carboxy'lic-acid esters by selectiveadduct-iormation "with urea and to a method based thereon for thesegregation of various types of organic acids. In one specificembodiment, our invention relates to the segregation and separation 'ofstraight-chain and monomethyl-branched aliphatic carboxylic acids fromadmixture with other organic acids.

Our invention is based on our discovery that urea rorms solid adductswith certain monomethyl-branched esters, as hereinafter defined, whereasit does not form adducts with more highly branched esters. By use ofthis selective reaction, in combination with other process steps to bedescribed more fully hereinafter, we are now able to segregate mixturesof organic acids into three fractions, consisting of (1) straightchainaliphatic carboxylic acids, (2) monomethyl-branched aliphatic carboxylicacids, and (3) other organic acids.

According to the prior art, urea forms solid adducts with numerousstraight-chain organic compounds, including hydrocarbons, alcohols,aldehydes, ketones, and n-alkanoic acids and their ethyl esters; andthis reaction has been utilized for the separation of suchstraight-chain compounds from admixture with other organic compounds. Wehave observed, however, that the reaction of urea with alkanoic acids isnot selective for the n-alk'anoic acids. Instead, urea reactsindiscriminately with alkano'ic acids in general, evolving heat andforming a hard cake, rather than the crystalline adduct ordinarilyobtained with straight-chain organic compounds. The separation oforganic acids by this technique is therefore not feasible.

We have now made the surprising discovery, which the prior art nowherediscloses or suggests, that the formation of solid urea adducts withcarboxylic acid esters is a highly selective reaction, being dependentupon the extent and position of branching, the position or thecharacteristic carbonyloxy group, the length of the straight carbonchain or chains attached to the carbonyloxy group, and the nature of anyother substituents in the ester molecule. It is known that urea adductsare formed with certain straight-chain ethyl esters, whereas adducts arenot formed with esters of cyclic acids or with esters containing cyclicsubstituents in the molecule. We have now discovered that urea formsadducts with monomethyl-branched esters "wherein the straight-chainterminal pen tion on nt'a'ining the characteristic carbcn group Icontains also a total of at least four methylene roups, whereas ureadoes not form adducts with more highly branched esters (that is. estersbranched esters may be represented bytne' generic skeletal formula lat-Ewhere R is a straight-chain aliphatic raditai and E is a tem'inaistraight-chain ester group having one of the following skeletalformulas:

where :c and y are zero or a positive integer, where the sum of :c and yis at least four, and where '63: and 0,, respectively represent straightcarbon chains when a: or y is greater than one; Inthe above formulas,the otherwise unsatisfiedbonds of the carbon atoms are in generalattached to hydrogen atoms, but we have further observed that theadduct-forming capacity or esters is substantially unaffected by thepresence in the molecule of an olefinic double bond,- and/or a hydroxylgroup, and/or a fluorine atom.-

(3n the basis of the foregoing observations, we have now devised a newprocess involving the selective reaction of urea with esters, by meansof which we are able to efiect the segregation and separation ofstraight-chain and monomethylbranched aliphatic carboxylic acids fromadmixture with other organic acids. Mixtures oi such acids and/or estersmay be diflicult or impossible to separate by conventional means, suchas fractional distillation, fractional crystallization, and the like,owing to their close similarity of physical and chemical properties. 4}

We have further discovered that the selective reaction of urea withesters, as defined herein,

organic-acid fractions of special characteristics and high utility fromcomplex mixtures thereof with other organic compounds. Other objects ofA still.

Another object of our invention is to V our invention, and itsadvantages over the prior art, will be apparent from the followingdescription, examples, and claims.

In a simple embodiment, our invention may be used to process a chargingstock comprising a n-alkyl ester of a monomethyl-branched alkanoic acidhaving the following structural formula OH: I A R( JH(CHz),-!JO(CHfl-CH; where R is n-alkyl, a: and y are zero or a positive integer, andthe sum of a: and y is at least four. The charging stock is agitatedwith urea, preferably in the presence of a urea activator such as water,and the resulting slurry is filtered, centrifuged, or settled anddecanted to separate the solid adduct therefrom. The adduct thusseparated contains urea and the ester defined above; and if otherurea-reactive substances such as straight-chain organic compoundscontaining six or more carbon atoms in the molecule, or free carboxylicacids, were absent from the charging stock, the adduct contains theurea-reactive ester in substantially pure form. The adduct may be washedwith an'inert organic liquid, such as a branched-chain, naphthenic, oraromatic hydrocarbon, having substantially no reactivity with orsolvency for urea, in order to remove occluded mother liquor therefrom;and may thereafter be decomposed to liberate the desired ester.

In carrying out the above process, the charging stock may first bedissolved in an inert organic liquid, such as a branched-chain,naphtheme, or aromatic hydrocarbon. This is especially desirable wherethe charging stock is a viscous liquid or a solid. The quantity of urearequired may be calculated on the basis of the quantity ofadduct-forming ester in the charging stock. The molar ratio of urea tosuch ester is preferably at least equal to the total number of methylenegroups in the ester group E, defined above, of

the urea-reactive ester.

In the reaction mixture or in the urea may advantageously beincorporated a urea activator, preferably water, methanol, ethanol,acetone, propionaldehyde, or other lower aliphatic alcohol, loweraliphatic aldehyde, or lower aliphatic ketone. Other organic oxygenatedcompounds mayaso be used as urea activators, such as amyl acetate, ethylether, methyl n-amyl ketone, ndodecyl alcohol, z-ethyl-l-hexanol,l-octanol, and the'like; but they are not in general as effective as thepreferred activators recited above. The molar ratio of activator to ureamay range up to the quantity required to form a saturated solution ofurea therein. Excellent results may be obtained, for example, Within therange of about 0.05:1 to 1:1, but we prefer to operate between about0.1:1 and 0.621. The reaction temperature is not critical, but should behigh enough to maintain the charging stock in liquid form, and lowenough to avoid melting and decomposing the urea adduct. Temperaturesbetween about 0 and C. are ordinarily satisfactory, but We prefer tooperate between about 20 and 75 C. The time of contact between the ureaand the charging stock is likewise not a critical variable. Adductformation begins to take place almost instantaneously, and may bevirtually complete in as little as 0.1 hour in some cases, especiallywhen a urea activator is employed. We prefer in general to contact thereactants for a reaction period ranging from about 0.25 to 1.0 hourinorder to insure substantially complete reaction between urea andester.

,Decomposition of the urea adduct and liberation of ester may beeffected by dissolving the adduct in an excess of a urea solvent, suchas water, methanol, ethanol, acetone, and the like, at a temperatureabove the melting point of the ester. We prefer to use water since theester liberated thereby separates as a second phase from the resultingaqueous solution of urea. Alternatively, we may decompose the adduct byheating it to a temperature above its melting point, ordinarily aroundC. The ester is liberated thereby as a separate phase, which may bewithdrawn. Thereafter, the ester may be decomposed according towell-known procedures .to regenerate the fatty-acid constituent thereofin purified form, or the ester may be subjected to radical interchangewith an alcohol or an acid to produce a different ester species.

In anotherembodiment of our invention, we may contact urea with acharging stock containing a monomethyl-branched alkyl ester of astraight-chain aliphatic carboxylic acid having the structural formulaCH; O

R-cn oH, ,-o- J- on2)roe. whereR is n-alkyl, x and y are zero or apositive integer, and the sum of. wand :11 is at least four, andseparating from the resulting slurry a urea adduct containing saidester: a

In another embodiment of our invention, we may contact a charging, stockcontaining monomethyl-branched alkyl esters of a mixture of organicacids with urea, and separate therefrom a solid urea adduct containingthe esters of the straight-chain aliphatic carboxylic acids having thefollowing structural formula CH3 0 RJ3H(CHz)-O&-(OH),UH; where R isn-alkyl, a: and y are zero or a positive integer, and the sum of ac andy is at least four. We may thereafter convert the esters in the depletedcharging stock into n-alkyl esters, and again treat the charging stockwith urea. Adducts are thereby formed containing esters ofmonomethyl-branched aliphatic carboxylic acids having the followingstructural formula CH: O R-oH on) it-owhere R is n-alkyl, a: and y arezero or a positive integer, and the sum of x and y is at least four.This adduct is separated, leaving behind any other types of estersoriginally contained in the charging stock. 7 s

In another embodiment of our invention, we

may contact a charging stock containing n-alkyl esters :ci ahflxhme ofarseniceemsrwithiurea. and separate therefrom a. solid .ureaxadductformed from the estersoi: the'naalkanoieiacids contained therein havingthe structural formula on-aonnfio oqsun en, where a d y are zero. or aposi ve, intes n'and the spin o w n a s a 'leasttoun; and ancesto s of;the ..monoinethyl-branched n-alkanoic acids contained ther n having thestructural fiql li l on. o R-JJH'-(Cfim b wfifl fifli where R isn-alkyl, a; and'yarezeroor'a positive integer, and the sumof'ar' and 1;is at least four. leaving behind. any other? types of .aestcrs oriinally'contained inthe chargingtstock. We may thereafter decomposethe'ureaadduct toliberate the mixed esters, which may then be convertedinto .monomethyl-branched alkyl esters and again treated with urea.Ureaiiadducts ."are. thereby formed containing n-zalkanoicsacid estershaving the following-structural formula CH: O R.J:H(CHz 1-(QH2)r-CHawhere R is n-alkyl, a: and y are zero or a positive integer, and the sumof a: and y is at least four. These adducts maybe withdrawn, leavingbehind the esters of the monomethyl-branched.

n-alkanoic acids.

It .will be apparent that mixtures of organic acids may be processedaccording to the procedures described above'simply by converting theacids first into the specified esters, containing aliphatic radicals ofthe desired configurations on each side of the carbonyloxygroup. We may,for example, convert a mixture of organic acids into monomethyl-branchedaliphatic esters uch as isopr pyl. isobutyl. isopcnty 2-m thy buty.1.i-methyl-z-butenyl, isoheptyl, l-m hylhepty isotetradecyl. andisooctadecyl ster and th like, by heating the mixture of acids with analcohol affording a mQnOmethyI-branched aliphatic radical, suitably astraight-chain 2-alkanol, straight-chain alkene-z-ol, monomethylbranchedl-alkanol, or monomethyl-branched alkene-l ol, in the presence of anacidic esterification catalyst such as sulfuric acid or toluenesulfonicacid, whileremovins the water of reaction as an azeotrope with thealcohol or with an entrainingagent such as benzene, toluene, or thelike. When the esterification is complete, the acidic catalyst may beremoved by neutralization and water-washing, and the esters may bepurified if desired by distillation toremove non-esterified constituentsof the original charging stock. Thereafter, the mixture of esters may betreated with urea, the adduct separated, "the depleted ester mixtureconverted into esters of an alcohol affording a straight-chain aliphaticradical, and again treated with urea, as set forth above.

It is to be distinctly understood that the term monomethyl-branchedaliphatic radical" includes radicals of the type derivable fromsecondary straight-chain aliphatic alcoholshaving the 'hydroxyl group inthe 2 position. Such radicals have the skeletal confi uration 4 whereCa: represents astraight carbon chain.

The following is an especially useful embodimentor m ttresses-wh rebynarcoti adesubstantially-pore tern e nreiea ed irom straightsohaln leetsnc (n rmal hex-a is.c ne A hareine sto k containin st aight chainl-cetene is reacted with carbon monoxide and hydrogen in the. presenceof a o a t'c taly undQIQKW m OQQSS conditions to produce a who tune ofmarearic. l ehyde n he ade .y kie hyde),

more highly branched aldehydes. This mixture is fractional y d stilledto separate. he mix acid, or may advantageously be convertedby esterinterchange with glycerol into glycerol trimargarate, more commonlyknown as intarvin, a synthetic fat that is highly useful as a partial ortotal replacement for naturally occurring fats in the diet of diabetics.

Our invention may also be employed to advantage for separating thefatty-acid components of various naturally occurring esters, waxes,fate, or the like, for example, degras, which contains n-alkanoic,isoalkanoic, and anteisoalkanoic acid esters. Similarly, our inventionmay be used to separate the mixtures of fatty'acids obtained in theoxidation of hydrocarbons by various methods, and by the hydrogenationof carbon monoxide in the Fischer-Tropsch process and the numerousmodifications thereof.

In general, our invention is useful for segregating mixtures of organicacids into the following three groups: (1) n-alkanoic acids, such asacetic, propionic, butyric, valeric, caproic, enanthic, caprylic,pelargonic, capric, lauric, myristic, pale mitic, margaric, stearic, andlignoceric' acids and the like; n-alkenoic acids, such as acrylic,crotonic, 4-pentenoic, 2-hexenoic, 2-heptenoic, 3- heptenoic,i-heptenoic, 5-dodecenoic, and oleic acids, and the like; and themonohydroxy and monofiuoro derivatives of such n-alkanoic andn-allgenoicacids; (2) isoalkanoic acids, such ,as isobutyric,isovaleric, isocaproic, isoheptanoic, 8- methylnonanoic,IZ-methyltridecanoic, lfi-methe ylheptadecanoic, and26-methylheptacosanoio acids, and the like; anteisoalkanoic acids, suchas B-methylpentanoic, 6-methy1octanoic, B-methyldecanoic,IZ-methyltetradecanoic acids, and the like; other monomethyl-branchedalkanoic acids, such as 2-methylpentanoic, 5-1nethy1capric, '2- methylnyristic and 2-methylpalmitic acids, and the like; and counterparts ofthe foregoing groups containing a single olefinic double bond, at singlehydroxy group, and/or a single substituted fluorine atom; and (3) otherorganic acids.

Our invention will be more fully understood from the following specificexamples. All of the quantities of materials used herein are set forthin terms of parts by weight.

Example I .A solution of 0.644 part of methyl myristate in 312; parts ofneohexane was commingled with six -partsof urea and 0.79 part ofmethanol, and the alpha methflhexedc y d hyde. an

7 mixture was agitated at room temperature for one-half hour. Theresulting slurrywas filtered and the solid was washed with foursuccessive portions of neohexane, each portion weighing 3.24 parts.

The filtrate and washings were combined and evaporated to dryness.Unreacted methyl myristate weighing 0.015 part was recovered thereby,amounting to only 2.3 percent of the material originally charged.

The washed solid was dried and dissolved in 20 partsof water, and theresulting solution was exhaustively extracted with ethyl ether. Theether solution was then evaporated to dryness, and 0.604 part of methylmyristate was recovered therefrom. Thus, it was shown that a urea adducthad been formed by 94.8 percent of the methyl myristate originallycharged.

Example II A neohexanc solution containing 0.7850 part of isopropylmyristate was contacted with urea and methanol as described in ExampleI. From the urea adduct was recovered 0.687 part of the ester,corresponding to 87.5 percent of the charging stock. From the filtrateand washings was recovered 0.0731 part of ester, corresponding to 9.3percent.

' Example III A neohexane solution containing 0.7355 part ofZ-ethylhexyl myristate was contacted with urea and methanol as describedin Example I. From the filtrate and washings 0.721 part of the ester wasrecovered, corresponding to 98.1 percent of the charging stock. Thus,not more than 1.9 percent of the charging stock formed an adduct withthe urea. 7

Example IV A neohexanesolution containing 0.762 part of methyld-IZ-methyltetradecanoate was contacted with'urea. and methanol asdescribed in Example I. The resulting urea adduct yielded, on beingdecomposed, 0.666 part of the ester, corresponding to 87.4 percent ofthe quantity originally charged.

Example VI A neohexane solution containing 0.7415 part of isopropyld-lZ-methyltetradecanoate was treated with urea and methanol asdescribed in Example I. Only 0.0737 part of the ester was recovered fromthe urea adduct, corresponding to 10.0 percent of the charging stock.From the filtrate and washings was recovered 0.609 part of the ester,

corresponding to 82.1 percent.

Example VII A neohexane solution containing 0.267 part of methylisopalmitate, 0.287 part of isopropyl myristate, and 0.278 part ofmethyl d-12-methyltetradecanoate was contacted with urea and methanol asdescribed in Example I. From the resulting urea adduct was recovered0.647 part of esters, corresponding to 77.7 percent of the estersoriginally charged. From the filtrate and washings was recovered 0.183part of esters, corresponding to 22.0 percent.

Example VIII Heat of Comp nd Reaction k-calJmolcl2-Methyl-l-tetradecano1 2. 86 l2-Methyltetradecyl acetate 7. 7

Methyl IZ-methyltetradecanoate Thus, it is apparent thatmonomethyl-branched esters are much more reactive with urea thanmonomethyl-branched alcohols; and it is further apparent that theorientation of the carbonyloxy group is immaterial.

Example X n-Butyl n-butyrate formed an adduct of low stability whencontacted with methanol-activated urea. n-Butyl isobutyrate failed toreact with methanol-activated urea.

Example XI C'alorimetric tests were conducted in a conventional manneron the methyl and isopropyl esters of a group of saturated andmonoolefinic fatty acids to compare their heats of reaction withmethanol-activated urea. In each test, 6 parts of ester in parts ofsolvent were contacted in the calorimeter with parts of urea. Whensolvents other than methanol were used, 6 parts of methanol wereincorporated in the reaction mixture to activate the urea. The resultswere as follows:

Heat of Reaction, AH, k.-cal./mole Total OH: Groups, 20H:

Isooctane do l A number ofthe adductsobtained. in the above 1'0'limitedito the. chargmgstocks, manipulativesteps. orprocessconditionsemployed-therein, Durinvention is to be.construed broadlxwit th s p f thdescr t on a d cl maan any modifications orequivalents that vrouldordnenl occur to those skilled. in the. art areto beaconwith urea. Theresults were as follows: 'sideredas lying within the scope ofour 9E1.

Heat of Reaction, AH I a Acid Ester c fic I Uncor'rL, Conn,-k.-cal"./mol ek.-ca1./mole kscaL/mole All-Eicosenoic Methyl 93.6 21.22.7 I I 2' Do. IsopropyL. 60.0 15.5 25.9 1. 62 Erucic--- Methyl 92.223.7 25.6-. 1.42.

0.; Isopropyl 84.7 19.5 23.0 l;28

Thus, there appears to be no substantial dif- In accordance with. the.ioreeolns description. ference between com-parable methyl and isoi ropylwe aim as our in ention; esters as to their heats of add-uetformation.In- '20 1. A process for separating a monomethylstead, there appears tobe an equilibrium in the branched aliphatic ester wherein the straig r1;- urea-ester reactionthat is somewhat less ftworchain terminalportionv containing the characable toward adducts of isopropyl estersthan teristic carbonyloxy group toward adducts of corresponding methylesters. 0

Example XII i A hydroca bo p ase, p oduced by hyd enatcontains also atotalof at ea t four m thylen ing carbon monoxide in the presence of afluidroups. from a mixture thereorv with 3,IP. Q' an; lzed,alkali-promoted iron catalyst at approxicompound .WhlGlh 10.6.5 not rectwith urea, h mately 600 F. and 25.0 pounds per square inch, comprisescontact g said re ur.

was washed with dilute aqueous sodium hydroxide solution to remove theorganic acids. therefrom, and the organic acids were subsequentlyregenerated by sulfuric acid treatment and were separated from theaqueous extract. The resulting Example XIII The ClQ-C23 fraction of themixture of organic acids described in Example XII was converted into themethyl esters, and a neohexane solution containing 0.839 part of themethyl esters was treated with urea and methanol as described in ExampleI. From the resulting urea adduct was recovered only 0.055 part of theesters, corresponding to 6.5 percent of the esters charged. From thefiltrate and washings was recovered 0.780 part of esters, correspondingto 93.0 percent.

Example XIV Another portion of the Clo-C23 acid fraction described inExample XIII was converted into the isopropyl esters, and a neohexanesolution containing 1.061 parts of the isopropyl esters was contactedwith urea and methanol as described in Example I. From the resultingurea adduct was recovered only 0.044 part of the esters, correspondingto 4.1 percent of the esters originally charged. The combined filtrateand washings yielded 0.988 part of the esters on being evaporated,corresponding to 93.1 percent.

While we have described our invention with reference to a number ofspecific embodiments thereof, it is to be understood that we are notwithdrawin a solid addu t conta nin and said ster. substa tiall frezfmmsa d-wee reactive organic compound.

mp isesi contactin urea ianehed aliphatic este wh r in t stra n-11;.chain termimwl nortioncontaining the characteristic carbonyloxy groupcontains also a total of at least four methylene groups, whereby a solidadduct of urea and said ester is formed, and separating said adduct fromthe reaction mixture.

3. The process which comprises contacting urea and a urea solvent at atemperature between about 20 and 75 C. for a period in excess of around0.1 hour with a monomethyl-branched aliphatic ester wherein thestraight-chain terminal portion containing the characteristiccarbonyloxy group contains also at least four methylene groups, themolar ratio of urea to said ester being at least equal to the number ofsaid methylene groups, whereby a solid adduct of urea and said ester isformed, and separating said adduct from the reaction mixture.

4. In a process for separating a monomethylbranched carboxylic acid froma mixture thereof with a more highly branched organic acid, the stepswhich comprise (1) esterifying said acids with a primary monohydricstraight-chain alcohol of such a chain length that saidmonomethylbranched carboxylic acid is converted into amonomethyl-branched aliphatic ester wherein the straight-chain terminalportion containing the characteristic carbonyloxy group contains also atotal of at least four methylene groups, (2) contacting the esterifiedmixture with urea, (3) withdrawing a solid adduct containing urea andsaid monomethyl-branched ester, substantially free from ester of saidmore highly branched organic acid, (4) decomposing said adduct andrecovering the ester contained therein, and (5) decomposing therecovered ester and recovering said monomethyl-branched carboxylic acidtherefrom in purified form.

" 5 ma process forseparatinga mixture of organic acids containing astraight-chain and a branched-chain'carboxylic acid, the steps whichcomprised) esterifying said acids with an alcohol afiording amonomethyl-branche'd aliphatic radical of such a chain length that saidstraightchain acid is converted into a monomethylbranched aliphaticester wherein the straightchain terminal portion containing thecharacteristic carbonyloxy group contains also a total of at least fourmethylene groups, (2), contacting said esters with urea, (3) withdrawinga solid adduct containing urea and said monomethylbranched ester,substantially free from ester of said branched-chain carboxylic acid,(4) decomposing said adduct and recovering the ester containedtherein,and (5) decomposing the recovered ester and recovering saidstraight-chain carboxylic acid therefrom in purified form.

6. The process of claim 2 wherein said ester has the skeletal formulawhere R is a straight-chain aliphatic radical,

where a: andy are selected from the class consisting of zero and'thepdsitive integers, where the sum of a: and y is at least four, where Crrepresents a straight carbon chain when a: is greater than one, where Cyrepresents a straight carbon chain when y is greater than one, wheresaid ester contains not more than one olefinic double bond, not morethan one hydroxyl group,

and not more than one fluorine atom, and where otherwise unsatisfiedbonds of the carbon atoms are attached to hydrogen atoms.

12 7. The process of'claim 6 wherein said ester has the structuralformula 8. The process of claim 2 wherein said ester has the skeletalformula 0 o 7 R o-c,-0- -o,-o ,where R is a straight-chain aliphaticradical, where a: and y are selected from the class consisting of zeroand the positive integers, where the sum of a: and y is at least four,where C1 represents a straight carbon chain when a: is greater than one,where Cy represents a straight carbon chain when :1; is greater thanone, where said ester contains not more than one olefinic double bond,not more than one hydroxyl group,

and not more than one fluorine atom, and where otherwise unsatisfiedbonds of the carbon atoms are attached to hydrogen atoms.

9. The process of claim 8 wherein said ester has the structural formulaREFERENCES CITED The following references are of record in the file ofthis patent:

Bengen, Technical Oil Mission, Reel 143, frames 135-139, May 22, 1946.

4. IN A PROCESS FOR SEPARATING A MONOMETHYLBRANCHED CARBOXYLIC ACID FROMA MIXTURE THEREOF WITH A MORE HIGHLY BRANCHED ORGANIC ACID, THE STEPSWHICH COMPRISE (1) ESTERIFYING SAID ACIDS WITH A PRIMARY MONOHYDRICSTRAIGHT-CHAIN ALCOHOL OF SUCH A CHAIN LENGTH THAT SAIDMONOMETHYLBRANCHED CARBOXYLIC ACID IS COVERTED INTO AMONOMETHYL-BRANCHED ALIPHATIC ESTER WHEREIN THE STRAIGHT-CHAIN TERMINALPORTION CONTAINING THE CHARACTERISTIC CARBONYLOXY GROUP CONTAINS ALSO ATOTAL OF AT LEAST FOUR METHYLENE GROUPS, (2) CONTACTING THE ESTERIFIEDMIXTURE WITH UREA, (3) WITHDRAWING A SOLID ADDUCT CONTAINING UREA ANDSAID MONOMETHYL-BRANCHED ESTER, SUBSTANTIALLY FREE FROM ESTER OF SAIDMORE HIGHLY BRANCHED ORGANIC ACID, (4) DECOMPOSING SAID ADDUCT ANDRECOVERING THE ESTER CONTAINED THEREIN, AND (5) DECOMPOSING THERECOVERED ESTER AND RECOVERING SAID MONOMETHYL-BRANCHED CARBOXYLIC ACIDTHEREFROM IN PURIFIED FORM.